Optical imaging system including seven lenses of +--- +-+ or +--++-+ refractive powers

ABSTRACT

An optical imaging system includes a first lens, a second lens, a third lens, a fourth lens, a fifth lens having a convex image-side surface, a sixth lens, and a seventh lens disposed in order from an object side, and a distance from the image-side surface of the fifth lens to an object-side surface of the sixth lens is shorter than a distance from an image-side surface of the sixth lens to an object-side surface of the seventh lens.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 USC 119(a) of Korean PatentApplication No. 10-2018-0081061 filed on Jul. 12, 2018, in the KoreanIntellectual Property Office, the entire disclosure of which isincorporated herein by reference for all purposes.

BACKGROUND 1. Field

The following description relates to an optical imaging system capableof implementing constant optical performance irrespective of changes inambient temperature.

2. Description of Background

Generally, surveillance cameras provided in vehicles have been used toimage only shapes of surrounding objects, and it has not been necessaryto design surveillance cameras to provide high resolution images.However, as a self-driving function has recently been provided invehicles, there has been demand for an optical system appropriate for acamera which can image objects at a long distance or can provide clearerimages of objects at short distance.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

In one general aspect, an optical imaging system includes a first lens,a second lens, a third lens, a fourth lens, a fifth lens having positiverefractive power, a sixth lens, and a seventh lens disposed in orderfrom an object side. At least one of the lenses includes one or moreaspherical surfaces, and a distance from an object-side surface of thefirst lens and to an imaging plane is 20 mm or greater.

The first lens may have positive refractive power.

The third lens may have negative refractive power.

The sixth lens may have negative refractive power.

The third lens may include a concave image-side surface.

The fourth lens may include a concave object-side surface.

The fifth lens may include a convex image-side surface.

The sixth lens may include a concave object-side surface.

The sixth lens may include a concave image-side surface.

The seventh lens may include a convex image-side surface.

In another general aspect, an optical imaging system includes a firstlens, a second lens, a third lens, a fourth lens, a fifth lens having aconvex image-side surface, a sixth lens, and a seventh lens disposed inorder from an object side. A distance from the image-side surface of thefifth lens to an object-side surface of the sixth lens is shorter than adistance from an image-side surface of the sixth lens to an object-sidesurface of the seventh lens.

A distance from an object-side surface of the first lens to an imagingplane may be 20 mm or greater.

Three or more of the lenses may have refractive indexes of 1.7 orgreater.

One surface of a lens, among the lenses, disposed most adjacent to theobject side or most adjacent to an imaging plane may be aspherical, andone surface of a lens, among the lenses, adjacent to a stop may beaspherical.

The third lens, the fourth lens, and the fifth lens may each have arefractive index of 1.7 or greater.

The first lens may have positive refractive power.

An Abbe number of the third lens may be within a range of 20 to 45.

A sum of an Abbe number of the third lens and an Abbe number of thesecond lens may be within a range of 60 to 100.

The optical imaging system may have an F No. of 1.45 or less.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a first example of an optical imagingsystem.

FIG. 2 illustrates aberration curves of the optical imaging systemillustrated in FIG. 1.

FIG. 3 illustrates MTF curves of the optical imaging system illustratedin FIG. 1 depending on temperature change.

FIG. 4 is a diagram illustrating a second example of an optical imagingsystem.

FIG. 5 illustrates aberration curves of the optical imaging systemillustrated in FIG. 4.

FIG. 6 illustrates MTF curves of the optical imaging system illustratedin FIG. 4 depending on temperature change.

FIG. 7 is a diagram illustrating a third example of an optical imagingsystem.

FIG. 8 illustrates aberration curves of the optical imaging systemillustrated in FIG. 7.

FIG. 9 illustrates MTF curves of the optical imaging system illustratedin FIG. 7 depending on temperature change.

FIG. 10 is a diagram illustrating a fourth example of an optical imagingsystem.

FIG. 11 illustrates aberration curves of the optical imaging systemillustrated in FIG. 10.

FIG. 12 illustrates MTF curves of the optical imaging system illustratedin FIG. 10 depending on temperature change.

FIG. 13 is a diagram illustrating a fifth example of an optical imagingsystem.

FIG. 14 illustrates aberration curves of the optical imaging systemillustrated in FIG. 13.

FIG. 15 illustrates MTF curves of the optical imaging system illustratedin FIG. 13 depending on temperature change.

FIG. 16 is a diagram illustrating a sixth example of an optical imagingsystem.

FIG. 17 illustrates aberration curves of the optical imaging systemillustrated in FIG. 16.

FIG. 18 illustrates MTF curves of the optical imaging system illustratedin FIG. 16 depending on temperature change.

Throughout the drawings and the detailed description, the same referencenumerals refer to the same elements. The drawings may not be to scale,and the relative size, proportions, and depiction of elements in thedrawings may be exaggerated for clarity, illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent after an understanding of thedisclosure of this application. For example, the sequences of operationsdescribed herein are merely examples, and are not limited to those setforth herein, but may be changed as will be apparent after anunderstanding of the disclosure of this application, with the exceptionof operations necessarily occurring in a certain order. Also,descriptions of features that are known in the art may be omitted forincreased clarity and conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided merelyto illustrate some of the many possible ways of implementing themethods, apparatuses, and/or systems described herein that will beapparent after an understanding of the disclosure of this application.

Herein, it is noted that use of the term “may” with respect to anexample or embodiment, e.g., as to what an example or embodiment mayinclude or implement, means that at least one example or embodimentexists in which such a feature is included or implemented while allexamples and embodiments are not limited thereto.

Throughout the specification, when an element, such as a layer, region,or substrate, is described as being “on,” “connected to,” or “coupledto” another element, it may be directly “on,” “connected to,” or“coupled to” the other element, or there may be one or more otherelements intervening therebetween. In contrast, when an element isdescribed as being “directly on,” “directly connected to,” or “directlycoupled to” another element, there can be no other elements interveningtherebetween.

As used herein, the term “and/or” includes any one and any combinationof any two or more of the associated listed items.

Although terms such as “first,” “second,” and “third” may be used hereinto describe various members, components, regions, layers, or sections,these members, components, regions, layers, or sections are not to belimited by these terms. Rather, these terms are only used to distinguishone member, component, region, layer, or section from another member,component, region, layer, or section. Thus, a first member, component,region, layer, or section referred to in examples described herein mayalso be referred to as a second member, component, region, layer, orsection without departing from the teachings of the examples.

Spatially relative terms such as “above,” “upper,” “below,” and “lower”may be used herein for ease of description to describe one element'srelationship to another element as shown in the figures. Such spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. For example, if the device in the figures is turned over,an element described as being “above” or “upper” relative to anotherelement will then be “below” or “lower” relative to the other element.Thus, the term “above” encompasses both the above and below orientationsdepending on the spatial orientation of the device. The device may alsobe oriented in other ways (for example, rotated 90 degrees or at otherorientations), and the spatially relative terms used herein are to beinterpreted accordingly.

The terminology used herein is for describing various examples only, andis not to be used to limit the disclosure. The articles “a,” “an,” and“the” are intended to include the plural forms as well, unless thecontext clearly indicates otherwise. The terms “comprises,” “includes,”and “has” specify the presence of stated features, numbers, operations,members, elements, and/or combinations thereof, but do not preclude thepresence or addition of one or more other features, numbers, operations,members, elements, and/or combinations thereof.

Due to manufacturing techniques and/or tolerances, variations of theshapes shown in the drawings may occur. Thus, the examples describedherein are not limited to the specific shapes shown in the drawings, butinclude changes in shape that occur during manufacturing.

The features of the examples described herein may be combined in variousways as will be apparent after an understanding of the disclosure ofthis application. Further, although the examples described herein have avariety of configurations, other configurations are possible as will beapparent after an understanding of the disclosure of this application.

Hereinafter, examples will be described with reference to the attacheddrawings.

In the examples, an entirety of a radius of curvature, a thickness, anda focal length of a lens are indicated in millimeters (mm). Further, athickness of a lens, and a gap between lenses are distances measuredbased on an optical axis of the lens.

In a description of a form of a lens, a surface of a lens being convexindicates that an optical axis region of a corresponding surface isconvex, while a surface of a lens being concave indicates that anoptical axis region of a corresponding surface is concave. Therefore, ina configuration in which a surface of a lens is described as beingconvex, an edge region of the lens may be concave. In a similar manner,in a configuration in which a surface of a lens is described as beingconcave, an edge region of the lens may be convex.

In the examples, an optical imaging system may include a plurality oflenses. For example, the optical imaging system may include sevenlenses. In the descriptions below, the lenses of the optical imagingsystem will be described.

The first lens may have refractive power. For example, the first lensmay have positive refractive power.

The first lens may have a convex surface. For example, the first lensmay have a convex object-side surface.

The first lens may include a spherical surface. For example, bothsurfaces of the first lens may be spherical. The first lens may be madeof a material having high light transmissivity and excellentworkability. For example, the first lens may be made of a glassmaterial. However, a material of the first lens is not limited to aglass material.

The first lens may have a certain refractive index. For example, arefractive index of the first lens may be 1.7 or higher. The first lensmay have an Abbe number smaller than an Abbe number of the second lens.For example, an Abbe number of the first lens may be less than 55.

The second lens may have refractive power. For example, the second lensmay have negative refractive power.

The second lens may have a convex surface. For example, the second lensmay have a convex object-side surface.

The second lens may include a spherical surface. For example, bothsurfaces of the second lens may be spherical. The second lens may bemade of a material having a constant refractive index irrespective oftemperature change. For example, the second lens may be made of a glassmaterial.

The second lens may have a certain refractive index. For example, arefractive index of the second lens may be less than 1.60. The secondlens may have a certain Abbe number. For example, an Abbe number of thesecond lens may be within a range of 20 to 75.

The third lens may have refractive power. For example, the third lensmay have negative refractive power.

The third lens may have a convex surface. For example, the third lensmay have a convex object-side surface.

The third lens may include an aspherical surface. For example, at leastone of the object-side surface and the image-side surface of the thirdlens may be aspherical. The third lens may be made of a material havinghigh light transmissivity and excellent workability. For example, thethird lens may be made of a glass material. However, a material of thethird lens is not limited to a glass material.

The third lens may have a certain refractive index. For example, arefractive index of the third lens may be 1.80 or greater. The thirdlens may have a certain Abbe number. For example, an Abbe number of thethird lens may be within a range of 20 to 45. As another example, anAbbe number of the third lens may be within a range in which a sum of anAbbe number of the third lens and an Abbe number of the second lens iswithin a range of 60 to 100.

The fourth lens may have refractive power. For example, the fourth lensmay have positive refractive power or negative refractive power.

The fourth lens may have a concave surface. For example, the fourth lensmay have a concave object-side surface.

The fourth lens may include a spherical surface. For example, bothsurfaces of the fourth lens may be spherical. The fourth lens may bemade of a material having high light transmissivity and excellentworkability. For example, the fourth lens may be made of a glassmaterial. However, a material of the first lens is not limited to aglass material.

The fourth lens may have a certain refractive index. For example, arefractive index of the fourth lens may be 1.70 or higher. The fourthlens may have an Abbe number higher than an Abbe number of the thirdlens. For example, an Abbe number of the fourth lens may be 40 orhigher.

The fifth lens may have refractive power. For example, the fifth lensmay have positive refractive power.

The fifth lens may have a convex surface. For example, at least one ofthe object-side surface and the image-side surface of the fifth lens maybe convex.

The fifth lens may include a spherical surface. For example, bothsurfaces of the fifth lens may be spherical. The fifth lens may be madeof a material having high light transmissivity and excellentworkability. For example, the fifth lens may be made of a glassmaterial. However, a material of the first lens is not limited to aglass material.

The fifth lens may have a certain refractive index. For example, arefractive index of the fifth lens may be 1.7 or higher. The fifth lensmay have an Abbe number lower than an Abbe number of the fourth lens.For example, an Abbe number of the fifth lens may be lower than 60.

The sixth lens may have refractive power. For example, the sixth lensmay have negative refractive power.

The sixth lens may have a concave surface. For example, at least one ofthe object-side surface and the image-side surface of the sixth lens maybe concave.

The sixth lens may include a spherical surface. For example, bothsurfaces of the sixth lens may be spherical. The sixth lens may be madeof a material having a constant refractive index irrespective oftemperature change. For example, the sixth lens may be made of a glassmaterial.

The sixth lens may have a certain refractive index. For example, arefractive index of the sixth lens may be 1.70 or higher. The sixth lensmay have an Abbe number lower than Abbe numbers of adjacent lenses(which are the fifth lens and the seventh lens). For example, an Abbenumber of the sixth lens may be less than 30.

The seventh lens may have refractive power. For example, the seventhlens may have positive refractive power.

The seventh lens may have a convex surface. For example, at least one ofthe object-side surface and the image-side surface of the seventh lensmay be convex.

The seventh lens may include an aspherical surface. For example, bothsurfaces of the seventh lens may be aspherical. The seventh lens may bemade of a material having a constant refractive index irrespective oftemperature change. For example, the seventh lens may be made of a glassmaterial.

The seventh lens may have a certain refractive index. For example, arefractive index of the seventh lens may be 1.7 or less. The seventhlens may have an Abbe number higher than an Abbe number of the sixthlens. For example, an Abbe number of the seventh lens may be 50 orhigher.

Three or more of the first to seventh lenses may have refractive indexesof 1.7 or higher. For example, the third to fifth lenses may haverefractive indexes of 1.7 or higher.

The optical imaging system may include one or more aspherical lenses.For example, two or more of the first to seventh lenses may includeaspherical surfaces. For example, a lens disposed most adjacent to anobject side or an imaging plane, and a lens adjacent to a stop mayinclude aspherical surfaces. The optical imaging system satisfying theconditions above may be desirable to implement a high resolution and toimprove aberration. The aspherical surface may be represented byEquation 1 below.

$\begin{matrix}{Z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {Ar}^{4} + {Br}^{6} + {Cr}^{8} + {Dr}^{10} + {Er}^{12} + {Fr}^{14} + {Gr}^{16} + {Hr}^{18}}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

In Equation 1 above, “c” is an inverse of a radius of a curvature of arespective lens, “K” is a conic constant, “r” is a distance from acertain point on an aspherical surface of the lens to an optical axis,“A” to “H” are aspheric constants, “Z” (or SAG) is a height from acertain point on an aspherical surface of the lens to an apex of theaspherical surface in an optical axis direction.

The optical imaging system may include an image sensor. The image sensormay be configured to implement a high level of resolution. A surface ofthe image sensor may form an imaging plane on which a subject is imaged.

The optical imaging system may include a stop. The stop may be disposedbetween lenses. For example, the stop may be disposed between the thirdlens and the fourth lens. The stop may adjust the amount of lightincident to an image sensor. Lenses adjacent to the stop in the opticalimaging system may be configured to have relatively small radiuses ofcurvature. For example, an image-side surface of the third lens may havea radius of curvature smaller than a radius of curvature of anobject-side surface of the third lens, and an object-side surface of thefourth lens may have a radius of curvature smaller than a radius ofcurvature of an image-side surface of the fourth lens.

The stop may be configured to divide refractive power of the opticalimaging system in half. For example, overall refractive power of lensesdisposed in a front portion (an object side) of the stop may benegative, and overall refractive power of lenses disposed in a rearportion (an image side) of the stop may be positive. The arrangement ofthe lenses may be desirable to reduce an overall length of the opticalimaging system while widening a field of view of the optical imagingsystem.

The optical imaging system may include a plurality of filters. Thefilters may be disposed between the seventh lens and the image sensorand may remove elements which may degrade resolution. For example, thefilters may block light with infrared wavelengths. The filters may havecertain refractive indices. For example, the refractive indexes of thefilters may be 1.50 or higher. The filters may have certain Abbenumbers. For example, Abbe numbers of the filters may be 60 or higher.

The optical imaging system may be configured to significantly reducechanges in focal length caused by temperature. For example, three ormore lenses in the optical imaging system may be made of a glassmaterial. The optical imaging system may include an element which mayimprove mass production. For example, a distance between the sixth lensand the seventh lens may be configured to be greater than a distancebetween the fifth lens and the sixth lens.

The optical imaging system may have a constant resolution in relativelyhigh temperature or in relatively low temperature. Thus, the opticalimaging system may provide clear images even when the optical imagingsystem is installed in a place easily exposed to an external environmentsuch as front and rear bumpers of vehicles.

In the description below, an optical imaging system will be described inaccordance with examples.

An example of an optical imaging system will be described with referenceto FIG. 1.

The optical imaging system 100 may include a plurality of lenses havingrefractive power. For example, the optical imaging system 100 mayinclude a first lens 110, a second lens 120, a third lens 130, a fourthlens 140, a fifth lens 150, a sixth lens 160, and a seventh lens 170.

The first lens 110 may have positive refractive power, and may have aconvex object-side surface and a concave image-side surface. The secondlens 120 may have negative refractive power, and may have a convexobject-side surface and a concave image-side surface. The third lens 130may have negative refractive power, and may have a convex object-sidesurface and a concave image-side surface. The fourth lens 140 may havenegative refractive power, and may have a concave object-side surfaceand a convex image-side surface. The fifth lens 150 may have positiverefractive power, and may have a convex object-side surface and a conveximage-side surface. The sixth lens 160 may have negative refractivepower, and may have a concave object-side surface and a concaveimage-side surface. The seventh lens 170 may have positive refractivepower, and may have a convex object-side surface and a convex image-sidesurface.

The optical imaging system 100 may include a plurality of asphericallenses. In the optical imaging system 100, both surfaces of the thirdlens 130 and both surfaces of the seventh lens 170 may be aspherical.The optical imaging system 100 may include a lens made of a glassmaterial to exhibit constant optical performance even when temperaturechanges due to external conditions.

The optical imaging system 100 may include a stop ST. The stop ST may bedisposed between the third lens 130 and the fourth lens 140.

The optical imaging system 100 may include a plurality of filters 180and 182. The filters 180 and 182 may be disposed between the seventhlens 170 and an imaging plane 190. At least one of the filters 180 and182 may block infrared light, and the other may prevent contamination ofthe imaging plane caused by foreign objects.

The optical imaging system 100 may have a relatively low F No. Forexample, the optical imaging system 100 may have F No. of 1.40. Anoverall length of the optical imaging system 100 may be 65 mm.

Table 1 lists characteristics of the lenses of the optical imagingsystem 100, and Table 2 lists aspheric coefficients of the lenses of theoptical imaging system 100.

TABLE 1 Surface Radius of Thickness/ Refractive Abbe Focal No. NoteCurvature Distance Index No. Length 1 First 18.452 7.841 1.773 49.6031.8727 2 Lens 60 0.100 3 Second 20 1.200 1.487 70.40 −50.4263 4 Lens10.811 2.780 5 Third 18.601 4.561 1.822 24.00 −21.7957 6 Lens 8.1155.890 7 Stop Infinity 2.135 8 Fourth −11.932 5.119 1.755 52.30 −892.45539 Lens −14.389 0.100 10 Fifth 30.002 5.202 1.804 46.50 16.4047 11 Lens−21.718 0.417 12 Sixth −21.718 1.200 1.741 27.80 −16.2450 13 Lens 27.6222.252 14 Seventh 22.663 8.000 1.619 63.90 17.4016 15 Lens −17.769 3.00016 First Infinity 0.400 1.517 64.10 17 filter Infinity 3.000 18 SecondInfinity 0.500 1.517 64.10 19 filter Infinity 11.292 20 Imaging Infinity0.012 Plane

TABLE 2 Surface No. K A B C D 5 0 −1.02E−04 −1.52E−07  1.20E−09 — 6 0−1.92E−04 −9.40E−07 −2.55E−09 — 14 0 −3.41E−05  6.00E−08 −8.43E−11 — 150  3.30E−05  4.25E−08  3.02E−10 —

FIG. 2 illustrates aberration curves of the optical imaging system 100,and FIG. 3 provides graphs illustrating MTF characteristics of theoptical imaging system 100.

A second example of an optical imaging system will be described withreference to FIG. 4.

An optical imaging system 200 may include a plurality of lenses havingrefractive power. For example, the optical imaging system 200 mayinclude a first lens 210, a second lens 220, a third lens 230, a fourthlens 240, a fifth lens 250, a sixth lens 260, and a seventh lens 270.

The first lens 210 may have positive refractive power, and may have aconvex object-side surface and a concave image-side surface. The secondlens 220 may have negative refractive power, and may have a convexobject-side surface and a concave image-side surface. The third lens 230may have negative refractive power, and may have a convex object-sidesurface and a concave image-side surface. The fourth lens 240 may havepositive refractive power, and may have a concave object-side surfaceand a convex image-side surface. The fifth lens 250 may have positiverefractive power, and may have a convex object-side surface and a conveximage-side surface. The sixth lens 260 may have negative refractivepower, and may have a concave object-side surface and a concaveimage-side surface. The seventh lens 270 may have positive refractivepower, and may have a convex object-side surface and a convex image-sidesurface.

The optical imaging system 200 may include a plurality of asphericallenses. In the optical imaging system 200, both surfaces of the thirdlens 230 and both surfaces of the seventh lens 270 may be aspherical.The optical imaging system 200 may include a lens made of a glassmaterial to exhibit constant optical performance even when temperaturechanges due to external conditions.

The optical imaging system 200 may include a stop ST. The stop ST may bedisposed between the third lens 230 and the fourth lens 240.

The optical imaging system 200 may include a plurality of filters 280and 282. The filters 280 and 282 may be disposed between the seventhlens 270 and an imaging plane 290. At least one of the filters 280 and282 may block infrared light, and the other may prevent contamination ofthe imaging plane caused by foreign objects.

The optical imaging system 200 may have a relatively low F No. Forexample, the optical imaging system 200 may have F No of 1.40. Anoverall length of the optical imaging system 200 may be 65 mm. In theoptical imaging system 200, the third lens may have a size smaller thansizes of the other lenses, and thus, the third lens may be manufacturedin aspherical shape, and manufacturing costs thereof may be reduced.

Table 3 lists characteristics of the lenses of the optical imagingsystem 200, and Table 4 lists aspheric coefficients of the lenses of theoptical imaging system 200.

TABLE 3 Surface Radius of Thickness/ Refractive Abbe Focal No. NoteCurvature Distance Index No. Length 1 First 24.861 5.933 1.773 49.6045.166 2 Lens 77.49 0.200 3 Second 14.625 6.243 1.785 25.80 −35.803 4Lens 7.813 3.028 5 Third 77.518 1.200 1.810 40.90 −25.584 6 Lens 16.2385.044 7 Stop Infinity 1.682 8 Fourth −22.427 3.861 1.729 54.70 179.305 9Lens −20.533 1.011 10 Fifth 29.664 4.375 1.804 46.60 15.506 11 Lens−20.091 0.200 12 Sixth −20.925 1.200 1.785 25.80 −14.861 13 Lens 27.0083.356 14 Seventh 27.836 7.515 1.670 55.40 16.880 15 Lens −16.968 3.00016 First Infinity 0.400 1.517 64.10 17 filter Infinity 3.000 18 SecondInfinity 0.500 1.517 64.10 19 filter Infinity 13.253 20 Imaging Infinity−0.001 Plane

TABLE 4 Surface No. K A B C D 5 0 −8.82E−05 6.19E−07 −9.18E−10  — 6 0−3.57E−05 7.26E−07 1.38E−08 — 14 0 −1.99E−05 2.40E−08 1.55E−10 — 15 0 3.84E−05 3.95E−08 2.45E−10 1.41E−12

FIG. 5 illustrates aberration curves of the optical imaging system 200,and FIG. 6 provides graphs illustrating MTF characteristics of theoptical imaging system 200.

A third example of an optical imaging system will be described withreference to FIG. 7.

An optical imaging system 300 may include a plurality of lenses havingrefractive power. For example, the optical imaging system 300 mayinclude a first lens 310, a second lens 320, a third lens 330, a fourthlens 340, a fifth lens 350, a sixth lens 360, and a seventh lens 370.

The first lens 310 may have positive refractive power, and may have aconvex object-side surface and a concave image-side surface. The secondlens 320 may have negative refractive power, and may have a convexobject-side surface and a concave image-side surface. The third lens 330may have negative refractive power, and may have a convex object-sidesurface and a concave image-side surface. The fourth lens 340 may havenegative refractive power, and may have a concave object-side surfaceand a convex image-side surface. The fifth lens 350 may have positiverefractive power, and may have a convex object-side surface and a conveximage-side surface. The sixth lens 360 may have negative refractivepower, and may have a concave object-side surface and a concaveimage-side surface. The seventh lens 370 may have positive refractivepower, and may have a convex object-side surface and a convex image-sidesurface.

The optical imaging system 300 may include a plurality of asphericallenses. In the optical imaging system 300, both surfaces of the thirdlens 330 and both surfaces of the seventh lens 370 may be aspherical.The optical imaging system 300 may include a lens made of a glassmaterial to exhibit constant optical performance even when temperaturechanges due to external conditions.

The optical imaging system 300 may include a stop ST. The stop ST may bedisposed between the third lens 330 and the fourth lens 340.

The optical imaging system 300 may include a plurality of filters 380and 382. The filters 380 and 382 may be disposed between the seventhlens 370 and an imaging plane 390. At least one of the filters 380 and382 may block infrared light, and the other may prevent contamination ofthe imaging plane caused by foreign objects.

The optical imaging system 300 may have a relatively low F No. Forexample, the optical imaging system 300 may have F No. of 1.45. Anoverall length of the optical imaging system 300 may be 60 mm.

Table 5 lists characteristics of the lenses of the optical imagingsystem 300, and Table 6 lists aspheric coefficients of the lenses of theoptical imaging system 300.

TABLE 5 Surface Radius of Thickness/ Refractive Abbe Focal No. NoteCurvature Distance Index No. Length 1 First 17.71 7.318 1.775 49.6231.004 2 Lens 55.137 0.100 3 Second 20 1.632 1.519 52.19 −40.830 4 Lens10.004 2.135 5 Third 14.141 3.145 1.828 24.04 −26.850 6 Lens 7.772 4.3237 Stop Infinity 3.753 8 Fourth −12.737 4.755 1.807 45.53 −352.446 9 Lens−15.557 0.100 10 Fifth 34.976 4.657 1.807 46.57 16.430 11 Lens −20.0930.443 12 Sixth −20.152 1.200 1.746 27.77 −14.299 13 Lens 23.212 0.588 14Seventh 22.585 7.179 1.696 53.20 15.299 15 Lens −17.515 3.000 16 FirstInfinity 0.400 1.518 64.20 17 filter Infinity 3.000 18 Second Infinity0.500 1.518 64.20 19 filter Infinity 11.771 20 Imaging Infinity 0.000Plane

TABLE 6 Surface No. K A B C 5 0 −1.47E−04 −4.62E−07  2.66E−09 6 0−2.45E−04 −1.37E−06 −1.11E−08 14 0 −3.08E−05  7.85E−08 −2.00E−10 15 0 2.08E−05  4.59E−08  1.90E−10

FIG. 8 illustrates aberration curves of the optical imaging system 300,and FIG. 9 provides graphs illustrating MTF characteristics of theoptical imaging system 300.

A fourth example of an optical imaging system will be described withreference to FIG. 10.

An optical imaging system 400 may include a plurality of lenses havingrefractive power. For example, the optical imaging system 400 mayinclude a first lens 410, a second lens 420, a third lens 430, a fourthlens 440, a fifth lens 450, a sixth lens 460, and a seventh lens 470.

The first lens 410 may have positive refractive power, and may have aconvex object-side surface and a concave image-side surface. The secondlens 420 may have negative refractive power, and may have a convexobject-side surface and a concave image-side surface. The third lens 430may have negative refractive power, and may have a convex object-sidesurface and a concave image-side surface. The fourth lens 440 may havenegative refractive power, and may have a concave object-side surfaceand a convex image-side surface. The fifth lens 450 may have positiverefractive power, and may have a convex object-side surface and a conveximage-side surface. The sixth lens 460 may have negative refractivepower, and may have a concave object-side surface and a concaveimage-side surface. The seventh lens 470 may have positive refractivepower, and may have a convex object-side surface and a convex image-sidesurface.

The optical imaging system 400 may include a plurality of asphericallenses. In the optical imaging system 400, both surfaces of the thirdlens 430 and both surfaces of the seventh lens 470 may be aspherical.The optical imaging system 400 may include a lens made of a glassmaterial to exhibit constant optical performance even when temperaturechanges due to external conditions.

The optical imaging system 400 may include a stop ST. The stop ST may bedisposed between the third lens 430 and the fourth lens 440.

The optical imaging system 400 may include a plurality of filters 480and 482. The filters 480 and 482 may be disposed between the seventhlens 470 and an imaging plane 490. At least one of the filters 480 and482 may block infrared light, and the other may prevent contamination ofthe imaging plane caused by foreign objects.

The optical imaging system 400 may have a relatively low F No. Forexample, the optical imaging system 400 may have F No. of 1.45. Anoverall length of the optical imaging system 400 may be 60 mm. In theoptical imaging system 400, the fifth lens and the sixth lens may beconfigured as a cemented lens. However, when high reliability againsttemperature is required, the fifth lens and the sixth lens may beseparated from each other.

Table 7 lists characteristics of the lenses of the optical imagingsystem 400, and Table 8 lists aspheric coefficients of the lenses of theoptical imaging system 400.

TABLE 7 Surface Radius of Thickness/ Refractive Abbe Focal No. NoteCurvature Distance Index No. Length 1 First 19.452 6.869 1.773 49.6032.610 2 Lens 72.243 0.100 3 Second 20 3.123 1.517 52.20 −36.384 4 Lens9.181 1.977 5 Third 13.973 3.508 1.822 24.00 −30.139 6 Lens 7.921 2.9347 Stop Infinity 3.647 8 Fourth −11.656 3.940 1.803 45.50 −974.129 9 Lens−13.614 0.100 10 Fifth 31.021 5.152 1.804 46.60 13.144 11 Lens −14.8420.000 12 Sixth −14.842 1.200 1.741 27.80 −12.481 13 Lens 25.364 2.476 14Seventh 26.145 7.673 1.694 53.20 15.961 15 Lens −16.889 3.000 16 FirstInfinity 0.400 1.517 64.20 17 filter Infinity 3.000 18 Second Infinity0.500 1.517 64.20 19 filter Infinity 10.403 20 Imaging Infinity 0.000Plane

TABLE 8 Surface No. K A B C 5 0 −1.45E−04 −9.21E−07  3.86E−09 6 0−2.66E−04 −2.74E−06 −1.57E−10 14 0 −3.42E−05  5.80E−08 −1.51E−10 15 0 2.56E−05  3.35E−08  1.96E−10

FIG. 11 illustrates aberration curves of the optical imaging system 400,and FIG. 12 provides graphs illustrating MTF characteristics of theoptical imaging system 400.

A fifth example of an optical imaging system will be described withreference to FIG. 13.

An optical imaging system 500 may include a plurality of lenses havingrefractive power. For example, the optical imaging system 500 mayinclude a first lens 510, a second lens 520, a third lens 530, a fourthlens 540, a fifth lens 550, a sixth lens 560, and a seventh lens 570.

The first lens 510 may have positive refractive power, and may have aconvex object-side surface and a concave image-side surface. The secondlens 520 may have negative refractive power, and may have a convexobject-side surface and a concave image-side surface. The third lens 530may have negative refractive power, and may have a convex object-sidesurface and a concave image-side surface. The fourth lens 540 may havepositive refractive power, and may have a concave object-side surfaceand a convex image-side surface. The fifth lens 550 may have positiverefractive power, and may have a convex object-side surface and a conveximage-side surface. The sixth lens 560 may have negative refractivepower, and may have a concave object-side surface and a concaveimage-side surface. The seventh lens 570 may have positive refractivepower, and may have a convex object-side surface and a convex image-sidesurface.

The optical imaging system 500 may include a plurality of asphericallenses. In the optical imaging system 500, both surfaces of the thirdlens 530 and both surfaces of the seventh lens 570 may be aspherical.The optical imaging system 500 may include a lens made of a glassmaterial to exhibit constant optical performance even when temperaturechanges due to external conditions.

The optical imaging system 500 may include a stop ST. The stop ST may bedisposed between the third lens 530 and the fourth lens 540.

The optical imaging system 500 may include a plurality of filters 580and 582. The filters 580 and 582 may be disposed between the seventhlens 570 and an imaging plane 590. At least one of the filters 580 and582 may block infrared light, and the other may prevent contamination ofthe imaging plane caused by foreign objects.

The optical imaging system 500 may have a relatively low F No. Forexample, the optical imaging system 500 may have F No. of 1.45. Anoverall length of the optical imaging system 500 may be 65 mm.

Table 9 lists characteristics of the lenses of the optical imagingsystem 500, and Table 10 lists aspheric coefficients of the lenses ofthe optical imaging system 500.

TABLE 9 Radius Surface of Thickness/ Refractive Abbe Focal No. NoteCurvature Distance Index No. Length 1 First 28.346 5.708 1.773 49.6244.772 2 Lens 143.318 0.200 3 Second 12.811 4.647 1.785 25.72 −56.989 4Lens 8.37 2.720 5 Third 19.671 2.342 1.810 40.95 −19.735 6 Lens 8.3495.366 7 Stop Infinity 2.717 8 Fourth −17.45 3.336 1.729 54.67 152.976 9Lens −16.306 0.200 10 Fifth 28.788 4.227 1.729 54.67 17.445 11 Lens−21.382 0.200 12 Sixth −25.738 1.200 1.785 25.72 −16.206 13 Lens 25.6523.665 14 Seventh 27.376 7.920 1.670 55.43 16.752 15 Lens −16.795 1.00016 First Infinity 0.400 1.517 64.17 17 filter Infinity 17.452 18 SecondInfinity 0.500 1.498 66.95 19 filter Infinity 1.205 20 Imaging Infinity−0.006 Plane

TABLE 10 Surface No. K A B C D 5 0 −2.50E−04 1.39E−06 −5.61E−09 0 6 0−3.64E−04 1.36E−06 −2.67E−08 0 14 0 −2.36E−05 3.03E−08  1.20E−10 0 15 0 3.51E−05 4.91E−08  1.35E−10 1.72E−01

FIG. 14 illustrates aberration curves of the optical imaging system 500,and FIG. 15 provides graphs illustrating MTF characteristics of theoptical imaging system 500.

A sixth example of an optical imaging system will be described withreference to FIG. 16.

An optical imaging system 600 may include a plurality of lenses havingrefractive power. For example, the optical imaging system 600 mayinclude a first lens 610, a second lens 620, a third lens 630, a fourthlens 640, a fifth lens 650, a sixth lens 660, and a seventh lens 670.

The first lens 610 may have positive refractive power, and may have aconvex object-side surface and a concave image-side surface. The secondlens 620 may have negative refractive power, and may have a convexobject-side surface and a concave image-side surface. The third lens 630may have negative refractive power, and may have a convex object-sidesurface and a concave image-side surface. The fourth lens 640 may havepositive refractive power, and may have a concave object-side surfaceand a convex image-side surface. The fifth lens 650 may have positiverefractive power, and may have a convex object-side surface and a conveximage-side surface. The sixth lens 660 may have negative refractivepower, and may have a concave object-side surface and a concaveimage-side surface. The seventh lens 670 may have positive refractivepower, and may have a convex object-side surface and a convex image-sidesurface.

The optical imaging system 600 may include a plurality of asphericallenses. In the optical imaging system 600, both surfaces of the thirdlens 630 and both surfaces of the seventh lens 670 may be aspherical.The optical imaging system 600 may include a lens made of a glassmaterial to exhibit constant optical performance even when temperaturechanges due to external conditions.

The optical imaging system 600 may include a stop ST. The stop ST may bedisposed between the third lens 630 and the fourth lens 640.

The optical imaging system 600 may include a plurality of filters 680and 682. The filters 680 and 682 may be disposed between the seventhlens 670 and an imaging plane 690. At least one of the filters 680 and682 may block infrared light, and the other may prevent contamination ofthe imaging plane caused by foreign objects.

An overall length of the optical imaging system 600 may be 83.340 mm.

Table 11 lists characteristics of the lenses of the optical imagingsystem 600, and Table 12 lists aspheric coefficients of the lenses ofthe optical imaging system 600.

TABLE 11 Surface Radius of Thickness/ Refractive Abbe Focal No. NoteCurvature Distance Index No. Length 1 First 36.734 8.000 1.773 49.6257.698 2 Lens 189.071 0.200 3 Second 18.422 8.000 1.785 25.72 −56.878 4Lens 10.55 2.981 5 Third 23.783 3.345 1.810 40.95 −22.138 6 Lens 9.588.505 7 Stop Infinity 3.620 8 Fourth −57.018 5.561 1.729 54.67 55.718 9Lens −24.7 0.200 10 Fifth 31.009 4.235 1.729 54.67 21.940 11 Lens−31.148 0.200 12 Sixth −35.897 1.200 1.785 25.72 −18.740 13 Lens 25.2766.638 14 Seventh 31.303 8.000 1.670 55.43 20.730 15 Lens −22.378 1.00016 First Infinity 0.400 1.517 64.17 17 filter Infinity 19.556 18 SecondInfinity 0.500 1.498 66.95 19 filter Infinity 1.208 20 Imaging Infinity−0.009 Plane

TABLE 12 Surface No. K A B C D 5 0 −1.58E−04  4.68E−07 −7.44E−10 0 6 0−2.63E−04  3.57E−07 −1.16E−08 0 14 0 −8.26E−06 −5.61E−09  5.07E−11 0 150  2.18E−05 −3.94E−09  6.69E−11 1.01E−13

FIG. 17 illustrates aberration curves of the optical imaging system 600,and FIG. 18 provides graphs illustrating MTF characteristics of theoptical imaging system 600.

In the optical imaging systems described in the examples, focal lengthsof the first to seventh lenses may be determined within a certain range.For example, a focal length of the first lens may be within a range of25 mm to 65 mm, a focal length of the second lens may be within a rangeof −60 mm to 30 mm, a focal length of the third lens may be within arange of −35 mm to −15 mm, a focal length of the fourth lens may be −300mm or less or 50 mm or greater, a focal length of the fifth lens may bewithin a range of 10 mm to 25 mm, a focal length of the sixth lens maybe within a range of −25 mm to −10 mm, and a focal length of the seventhlens may be within a range of 10 mm to 25 mm.

According to the examples, an optical imaging system having an improvedresolution and improved aberration may be implemented.

While this disclosure includes specific examples, it will be apparentafter an understanding of the disclosure of this application thatvarious changes in form and details may be made in these exampleswithout departing from the spirit and scope of the claims and theirequivalents. The examples described herein are to be considered in adescriptive sense only, and not for purposes of limitation. Descriptionsof features or aspects in each example are to be considered as beingapplicable to similar features or aspects in other examples. Suitableresults may be achieved if the described techniques are performed in adifferent order, and/or if components in a described system,architecture, device, or circuit are combined in a different manner,and/or replaced or supplemented by other components or theirequivalents. Therefore, the scope of the disclosure is defined not bythe detailed description, but by the claims and their equivalents, andall variations within the scope of the claims and their equivalents areto be construed as being included in the disclosure.

What is claimed is:
 1. An optical imaging system comprising: a firstlens having a positive refractive power; a second lens having arefractive power; a third lens having a refractive power; a fourth lenshaving a refractive power; a fifth lens having a positive refractivepower; a sixth lens having a refractive power and a concave image-sidesurface in an optical axis region thereof; and a seventh lens having arefractive power, wherein the first to seventh lenses are sequentiallydisposed in ascending numerical order from an object side of the opticalimaging system toward an imaging plane of the optical imaging system,either one or both of an object-side surface and an image-side surfaceof the seventh lens is aspherical, a distance from an object-sidesurface of the first lens to the imaging plane is 20 mm or greater, thefirst to seventh lenses are the only lenses having a refractive power inthe optical imaging system, and the third lens, the fourth lens, and thefifth lens each have a refractive index of 1.7 or greater.
 2. Theoptical imaging system of claim 1, wherein the third lens has a negativerefractive power.
 3. The optical imaging system of claim 1, wherein thesixth lens has a negative refractive power.
 4. The optical imagingsystem of claim 1, wherein the third lens has a concave image-sidesurface in an optical axis region thereof.
 5. The optical imaging systemof claim 1, wherein the fourth lens has a concave object-side surface inan optical axis region thereof.
 6. The optical imaging system of claim1, wherein the fifth lens has a convex image-side surface in an opticalaxis region thereof.
 7. The optical imaging system of claim 1, whereinthe sixth lens has a concave object-side surface in an optical axisregion thereof.
 8. The optical imaging system of claim 1, wherein theimage-side surface of the seventh lens is convex in an optical axisregion thereof.
 9. The optical imaging system of claim 1, wherein thesixth lens is spaced apart from the seventh lens along an optical axisof the optical imaging system.
 10. The optical imaging system of claim1, wherein a distance from an image-side surface of the fifth lens to anobject-side surface of the sixth lens is shorter than a distance from animage-side surface of the sixth lens to the object-side surface of theseventh lens.
 11. The optical imaging system of claim 1, wherein threeor more of the first to seventh lenses each have a refractive index of1.7 or greater.
 12. An optical imaging system comprising: a first lenshaving a refractive power; a second lens having a refractive power; athird lens having a refractive power; a fourth lens having a refractivepower; a fifth lens having a positive refractive power; a sixth lenshaving a refractive power; and a seventh lens having a refractive power,wherein the first to seventh lenses are sequentially disposed inascending numerical order from an object side of the optical imagingsystem toward an imaging plane of the optical imaging system, either oneor both of an object-side surface and an image-side surface of theseventh lens is aspherical, a distance from an object-side surface ofthe first lens to the imaging plane is 20 mm or greater, the first toseventh lenses are the only lenses having a refractive power in theoptical imaging system, and the third lens, the fourth lens, and thefifth lens each have a refractive index of 1.7 or greater.
 13. Theoptical imaging system of claim 1, wherein an Abbe number of the thirdlens is within a range of 20 to
 45. 14. The optical imaging system ofclaim 1, wherein a sum of an Abbe number of the third lens and an Abbenumber of the second lens is within a range of 60 to
 100. 15. Theoptical imaging system of claim 1, wherein the optical imaging systemhas an F No. of 1.45 or less.